My son has recently started riding with me and I'd like to put a headset into his helmet so we can talk easier. If you have one that your not using please let me know what you have and what you want for it. Bike is a '91 GL1500.
If your not looking for a system to directly plug into the bike I have a Chatter Box GMRSX1 I would let go for $125.00 shipped. It works perfectly. This is not the bluetooth model. I had it when I owned my Shadow 1100. Do a Google search and read up on it.
Also, it sounds like you want to put your son on the back. I don't know how old he is or if you would be interested in arm rests. These are brand new. Had them for about 25 miles, wife didn't like them. $75.00.
And last but not least I have a Utopia backrest that is in perfect shape. $100.00 plus shipping. I bought a new seat from Hartco so don't need it any more.